The invention is relative to the use of microwaves in the spinning industry. The invention is also relative to a method for determining the band (fiber band, sliver, slubbing) mass (bulk) of a moved fiber structure in a spinning preparation machine. The invention is furthermore relative to a corresponding machine preparation machine and to a corresponding measuring device. The invention is also relative to the recognition of foreign matter in a textile fiber structure by means of microwaves.
In the spinning industry, an evened-out fiber structure is first produced, e.g., from cotton, in several process steps and finally a twisted yarn is produced as the final product. The spinning preparation machines such as cards [carding machines] and draw [drawing] frames, that are arranged in front of the yarn production, have the particular task of stabilizing (leveling out) the fluctuations in sliver mass of one or several slivers or fiber bands, designated in the following in a summarizing manner as fiber structure. To this end, e.g., sliver sensors are arranged on draw frames, which sensors measure the sliver mass or fluctuations in sliver mass and transmit this information to a regulating unit that appropriately regulates at least one of the drawing members of the drafting device. A draw frame that operates in accordance with such a regulating principle is, e.g., the RSB-D30 model of the RIETER company. Information about the fluctuations of sliver mass is desired in many instances even in unregulated draw frames. An appropriate sensor at the outlet of such a draw frame emits, e.g., an appropriate cutoff signal for the machine and/or a warning signal if a threshold value of the sliver mass is exceeded or dropped below.
In order to measure the sliver mass and fluctuations of sliver mass (band), mechanical scanning devices in particular are known that are used today in almost all appropriate machines. However, the dynamics of these mechanical sensors is no longer sufficient at delivery speeds of more than 1000 m/min. In addition, the necessary, strong mechanical compression in front of the mechanical sensor has a noticeably negative effect on the drawing capacity.
In addition to the mechanical scanning of the fluctuations of sliver mass, other scanning principles have been suggested. Thus, e.g., U.S. Pat. No. 2,942,303 and DE 44 45 720 A1 teach measuring the sliver thickness in a contactless manner with penetrating optical radiation. However, the precision of measuring in this instance is heavily influenced by the ambient influences, e.g., temperature, moisture and dirt. Moreover, the method is susceptible to dye and reflection properties of the fiber structure.
Other known contactless measuring methods are those that use ultrasound waves. Measuring methods that operate capacitively or pneumatically are also known. The use of X-rays or γ-rays has also been suggested. However, all these methods are sensitive to moisture. It is therefore not very useful that climatic influences such as the temperature and the relative atmospheric moisture can be compensated as a rule in order to minimize climatic influences. The problem of inherent yarn moisture can not be readily eliminated in this manner. It is only mentioned here that viscose has a moisture of approximately 13%, e.g., at 40% relative atmospheric moisture. At a relative atmospheric moisture of 90% this value rises to 25%. In addition, the yarn moisture can vary by up to 5% under steady ambient conditions in one and the same batch of cotton. Also, the upper cotton layers in a can delivered to a spinning preparation machine absorb more moisture than the layers under them. Moreover, the textile fibers absorb differing moisture due to the change of climatic conditions in a spinning mill—e.g., mornings vs. afternoons vs. evenings. The cited influences, for their part, greatly influence the measured result of the sliver mass and therewith the quality of regulation.
The invention has the problem of improving the substantially contactless determination of the band mass of a fiber structure and, in general, measurements on a fiber structure.